As shown in FIG. 1 for a conventional electric power system, power is fed from a transmission system 110 to consumers 130, via a substation 115 and a distribution system 120 (electric utility). Because conventional distribution systems have no or very limited generation resources, any outage at or upstream from a substation affects the entire distribution systems. The outages can be due to generator and transmission line failures, short-circuit, overloads, climate and severe weather conditions, and geological events. Usually, a topology of the distribution system is radial and unidirectional, with currents flowing from the substation through the breakers and switches to the consumers.
Each downstream feeder can have a circuit breaker at a feeder head, several normally closed switches, i.e., sectionalizing switches, along the feeder, and several normally open switches, i.e., tie switches, at intersections between adjacent feeders, see legend 150. One purpose of the breakers and switches is to isolate the outages from functional parts of the system.
The example distribution system includes two feeders Fdr-1, and Fdr-2. The feeder Fdr-1 has one breaker BR-1, and three sectionalizers SW-1-1, SW-1-2, SW-1-3. The feeder Fdr-2 has one breaker BR-2, and two sectionalizers SW-2-1, SW-2-2. There is a tie switch SW-12 between the Fdr-1 and Fdr-2.
Modern electric power systems can include generators powered by solar, wind, landfill gas, and diesel fueled generators, even in distribution systems. Small generators, such as natural gas fueled micro-turbines can be co-located with consumers. This alternative distributed generation (DG) can enable local energy self-sufficiency, e.g., during outages, provided the distribution system is properly designed to integrate the DG, such as enabling of bi-directional power flows.
In addition, “green” consumers are more energy aware, and may want to adjust their energy consumption dynamically, particularly in a smart grid. Therefore, in a modern electric power system, demand responsive resources (DRR) are increasingly common. DRR change power consumption patterns that potentially could affect how the distribution system is configured.
This opens up new issues for the operation and control of the distribution systems. The first issue is that many of the renewable power sources are weather and time dependent. Therefore, the distribution system needs to be flexible to best facilitate intermittent and time-dependent renewable power source. In addition, the operation of the distribution systems needs to be able to accommodate bidirectional power flows.
The second issue is that some renewable resource, such as solar panels, output DC current. Therefore, distribution system needs DC to AC inverters to integrate those generation resources into the system. However, inverter based generation sources have no or less inertia than conventional synchronous generators. Thus, the distribution system has less time to react to and avoid instability when a local outage occurs, e.g., a sudden lack of wind or sunshine Therefore, the beakers and switches must be operate at much higher switching rate to reduce the system reaction time, and capacities of power storages must be properly used to increase the inertia of the system.
Several methods are known for configuring distribution systems to achieve a specific objective. US 20070086123 describes configuring a power distribution network only upon detection of a short-circuit or overload. U.S. Pat. No. 8,805,598 describes a dynamic reconfiguration of distribution feeder circuit based on overload protection parameters. US 20120065804 describes real-time feeder configuration for load balancing in distribution system automation due to overload at transformers. US 20130257153 describes a method for switching power to one or more loads based on overload, efficiency and availability of power sources. Characteristically, the above prior art methods generally reconfigure the distribution system only in response to unanticipated events.
The prior art systems and methods generally configure distribution systems for specific situations or applications, such as faults, and load balancing. Those solutions do not provide adequate solutions for distribution systems with a large number of renewable DG and more energy aware consumers using DRR.
Therefore, there is a need for a distribution system that can be configured dynamically to increase reliability, and efficiency of power distribution among consumers.